Straightening machine and method for straightening a metal strip or a flat metal part

ABSTRACT

A straightening machine (1) and a method for straightening a metal strip or a flat metal part (16) by the straightening machine, having upper straightening rollers (3) in an upper roller mill (2) and lower straightening rollers (6) in a lower roller mill (5). The upper and lower straightening rollers form upper and lower roller mill planes with a straightening gap therebetween and act on the metal strip to be straightened. In a working position, the upper roller mill plane forms an operating angle to the lower roller mill plane. The straightening gap (11) is changed by adjusting the upper roller mill plane relative to the lower roller mill plane. Before or at the start of a straightening process, the upper and/or lower roller mill is put in a starting position with a widened straightening nip, at least until a front end of the material strip has entered the inlet of the working region and for the rest of the straightening process, the upper and/or lower roller mill is put in the working position.

TECHNICAL FIELD

The invention relates to a method for straightening a material strip ora flat material part composed of metal or another material which can beplasticized by means of a straightening machine as well as astraightening machine for straightening such a material strip or flatmaterial part.

The invention relates in general to a method and a straightening machinefor a metal strip or a flat metal part; therefore, for the purpose ofsimplification, only a “metal strip” or “metal part” is discussed, whichrefers to a material strip or a metal part composed of metal or anothermaterial which can be plasticized.

BACKGROUND

A straightening machine of the present type contains a number of upperstraightening rollers, which are mounted in an upper roller mill, and anumber of lower straightening rollers, which are mounted in a lowerroller mill. In this case, the upper and lower straightening rollers arearranged so that they form between an inlet and an outlet of thestraightening machine in an operating region between the upper and lowerroller mill a straightening gap in order, in an operating position inwhich an upper roller mill plane is parallel to a lower roller millplane or forms an operating angle, to act at least temporarily from topto bottom on the metal strip or metal part to be straightened and guidethis in an operating direction from the inlet to the outlet through thestraightening machine. The operating angle normally opens toward theoutlet; there are, however, special applications in the case of whichthe opening angle opens toward the inlet. The axes of the upperstraightening rollers in the upper roller mill and the axes of the lowerstraightening rollers in the lower roller mill lie at least in part,preferably all, in the upper or lower roller mill plane.

A change in the straightening gap is normally performed by a paralleldisplacement of the upper roller mill plane relative to the lower rollermill plane so that the straightening gap can be adapted to a thicknessof the metal strip or flat metal part to be straightened.

In the metal-processing industry, metal strips are often used which aresupplied as coils and are unwound from there for production. By windingup the strip material to form coils, as well as by possible previousthermal treatment and the like, unevenness and tensions arise in thestrip material which are inexpedient for further processing. Metalstrips are therefore, after unwinding from the coil, generally conductedthrough the straightening gap of a straightening machine of the presenttype so that the metal strip can be supplied flat and with a low degreeof tension for further processing. The same also applies to flat metalparts which should be made free from undesirable bending and tensionwhich are generated in particular also during punching, bending orcutting of the metal parts.

Straightening machines of the present type serve to do away with suchtensions and unevenness in metal strips or metal parts. The upper andlower straightening rollers are, for this purpose, arranged offset toone another along the straightening gap in such a manner that thematerial to be straightened is alternately bent around upward anddownward on the straightening rollers. The bending is performed in thenormal case so that the material at least at the first straighteningrollers is bent beyond its yield point so that undesirable bending andtension in the material are balanced out as completely as possible. Ifthe operating angle opens toward the outlet, as is usually the case, thematerial on the first straightening rollers of the straightening machineis highly plasticized. At each further straightening roller, thematerial is bent to a slightly lesser extent, and at the laststraightening roller, the material is usually no longer plasticized,i.e. only elastically deformed.

As a result of the narrow advancing of the straightening rollers and thesignificant reshaping caused as a result of the metal part or metalstrip during straightening, crushing can occur in the region of ends,edges or corners of the metal part or metal strip to be straightened,which crushing results in a tapering of the thickness or thecross-section of the metal strip or metal part. It has therefore beenproposed in DE 10 2015 102 271 A1 to set the straightening gap in theregion of the inlet of the straightening machine initially to apredetermined starting value which preferably corresponds approximatelyto the material thickness of the part to be straightened in order toavoid the above-mentioned crushing. Only after the metal part or metalstrip runs into the operating region of the straightening machine is anadvancing of the upper and/or lower straightening rollers to a presetend value for the straightening process performed. The advancing and/orplacing of the upper and/or lower straightening rollers for setting thestraightening gap is performed in this case by parallel displacement ofthe upper and/or lower roller mill to one another. It has, however, beenshown that an advancing and placing of the upper and/or lowerstraightening rollers for setting the straightening gap can only becarried out very late if the part to be straightened has already beentransported far into the straightening machine. This leads to it notbeing optimally possible to straighten the region around the front endof the part to be straightened.

SUMMARY

The object on which the invention is based is to propose a method forstraightening a metal strip or a flat metal part by means of astraightening machine as well as a straightening machine of theabove-mentioned type, with which the avoidance of crushing in the regionof a front end of the metal part or metal strip to be straightened isimproved alongside simultaneous, as optimal as possible straightening ofthe metal part or metal strip.

This object is achieved by a method for straightening a metal strip or aflat metal part by means of a straightening machine with one or more ofthe features disclosed herein as well as by a straightening machine withone or more of the features of disclosed herein. Preferred furtherdevelopment of the method are described below and, in the claims, alongwith advantageous configurations of the straightening.

The method according to the invention for straightening a material stripor a flat material part is performed by means of a straightening machinewith a number of upper straightening rollers in an upper roller mill anda number of lower straightening rollers in a lower roller mill, whichform a straightening gap between an inlet and an outlet of thestraightening machine in an operating region between the upper and thelower roller mill, wherein the upper and the lower straightening rollersin an operating position of the upper and lower roller mill act at leasttemporarily from top to bottom on the material strip or material part tobe straightened and guide it in an operating direction from the inlet tothe outlet of the operating region through the straightening machine,wherein at least a part of the axes of the upper straightening rollersspans an upper roller mill plane and at least a part of the axes of thelower straightening rollers spans a lower roller mill plane, which inthe operating position are parallel or at a predetermined operatingangle to one another, wherein, in order to change or set thestraightening gap, the upper roller mill and/or the lower roller millcan be adjusted relative to the respective other roller mill and isplaced at least into a starting position with widened straightening gapand can be advanced into the operating position.

Prior to or at the start of a straightening process the upper and/orlower roller mill is placed into the starting position at least until afront end of the material strip or material part has run into the inletof the operating region of the straightening machine, and for thefurther straightening process the upper and/or lower roller mill isadvanced into the operating position, wherein the metal strip or themetal part is guided in the operating direction through thestraightening gap of the straightening machine for the straighteningprocess.

According to the invention, the straightening gap during placing intothe starting position is widened to a greater extent at the inlet thatat the outlet, or is widened to a greater extent at the outlet than atthe inlet, i.e. the upper and/or the lower roller mill is adjusted insuch a manner that the angle between the two roller mill planes changes.

The straightening gap during placing into the starting position ispreferably widened to a greater extent at the inlet than at the outletif the operating angle opens toward the outlet or the upper roller millplane is parallel to the lower roller mill plane. If, in contrast, theoperating angle opens toward the inlet, the straightening gap duringplacing into the starting position is preferably widened to a greaterextent at the outlet than at the inlet.

The following method steps are preferably performed:

-   -   (A) placing the upper and/or lower roller mill into the starting        position; and    -   (B) advancing the upper and/or lower roller mill into the        operating position,

wherein method step B is performed when or after the front end of thematerial strip or material part has reached a predetermined position inthe operating region.

As a result of the method according to the invention, it is madepossible that the metal part or metal strip to be straightened can beintroduced into the straightening machine without crushing of the frontend, wherein the straightening result is improved over the prior art.This is because it can be achieved by angled adjustment of the upperroller mill plane with respect to the lower roller mill plane that thoseregions of the straightening gap, in which the greatest deformation ofthe material to be straightened occurs, are widened to a maximum extent,while the other regions of the straightening gap are widened to a lesserdegree or not at all, i.e. the front end of the item to be straightenedis also partially straightened in the starting position.

In the case of an operating angle which, as is usually the case, openstoward the outlet, the advancing of the upper and/or lower roller millinto the operating position can be carried out at an early stage so thatthe region of the front end of the metal strip or metal part is also atleast partially straightened without crushing of the front end arisingin this case. As a result of the change in the angle between the upperand lower roller mill plane during the advancing into the operatingposition, the upper and lower straightening rollers come into contactearlier with the metal strip or metal part to be straightened, inparticular with the region adjacent to the front end of the metal stripor metal part, as a result of which the straightening result for themetal strip or metal part is improved.

The upper straightening rollers in the upper roller mill are preferablyarranged in such a manner that the axes of all the upper straighteningrollers run in the upper roller mill plane. Alternatively, the upperroller mill plane is formed by the axes of a plurality, but not all theupper straightening rollers. For example, in the case of a first uprightupper straightening roller in the operating direction, the upper rollermill plane is formed by the axes of all the upper straightening rollerswithout the first upper straightening roller in the operating direction.

The lower straightening rollers in the lower roller mill are preferablyarranged in such a manner that the axes of all the lower straighteningrollers run in the lower roller mill plane. Alternatively, the lowerroller mill plane is formed by the axes of a plurality, but not all thelower straightening rollers. For example, in the case of a last loweredlower straightening roller in the operating direction, the lower rollermill plane is formed by the axes of all the lower straightening rollerswithout the last lower straightening roller in the operating direction.

In the operating position, the operating angle is, as is known per se,preferably formed in such a manner that the straightening gap in theregion of the outlet corresponds substantially to the thickness of themetal strip or metal part to be straightened and in the region of theinlet lies below the thickness of the metal strip or metal part. Inspecial cases, an operating angle is occasionally selected which isoriented in a reversed manner.

In some cases, the operating angle is equal to zero, i.e. the rollermill planes are parallel to one another, and the straightening gapcorresponds to the thickness of the material to be straightened or is alittle smaller than this.

The predetermined position preferably lies in the region of the inlet,or is determined by a location of one of the lower or upperstraightening roller in the operating direction, preferably by thelocation of a first, second, third, fourth or fifth lower or upperstraightening roller in the operating direction. The predeterminedposition along the operating direction thus forms a type of trigger forthe movement of the upper and/or lower roller mill into the operatingposition. The location of the predetermined position can in this case bespecified for the respective straightening machine or input and changedin a control unit of the straightening machine independently of themetal part or metal strip to be straightened, in particularindependently of its thickness.

The predetermined position is preferably determined by the location ofone of the first upper or lower straightening rollers in the operatingdirection so that the advancing into the operating position can beperformed at an early stage after the metal strip or metal part to bestraightened has run into the operating region of the straighteningmachine. Alternatively, the location of the predetermined position canalso be selected depending on the metal strip or metal part to bestraightened.

A further preferred configuration of the method according to theinvention is characterized in that the front end of the material stripor material part is detected by means of a sensor, preferably a physicalsensor, in particular an optical or inductive sensor. A sensor signal isgenerated by the sensor if the front end of the metal strip or metalpart passes or reaches the sensor. In response to the sensor signal, theupper and/or the lower roller mill can be moved immediately or with atime delay into the operating position.

The sensor is preferably formed as a light barrier which extendstransversely to the operating direction in a transport plane of themetal strip or metal part. The detection of the front end of the metalstrip or metal part can thus be performed in a simple and reliablemanner.

Alternative or preferably additionally, the sensor is arranged at apredetermined position and method step B is performed immediately afterdetection of the front end of the metal strip or metal part by thesensor. The upper and/or lower roller mill is thus moved immediatelyinto the operating position in response to the sensor signal generatedby the sensor.

In one preferred embodiment of the method, the arrangement of the sensoris performed at a spacing in the operating direction upstream of thepredetermined position, wherein a time delay is determined until thepredetermined position of the front end of the material strip ormaterial part is reached from a conveying speed of the material strip ormaterial part and the spacing between the sensor and the predeterminedposition, and method step B is performed with or after the end of thetime delay after detection of the front end of the material strip ormaterial part by the sensor. In particular if the predetermined positionis supposed to lie within the straightening machine, it is thus possibleas a result of the structural circumstances to arrange the sensor at aneasily accessible position at which an undisturbed measurement of thefront end of the metal strip or metal part can also be carried out.

The arrangement of the sensor is preferably performed directly in frontof the inlet of the straightening machine, as a result of which inparticular reliable measurement and good accessibility are enabled atall times and it is possible to operate with a short time delay.

The placing of the upper and/or lower roller mill into the startingposition is preferably performed in such a manner that the straighteninggap in the region of the inlet corresponds at least to the thickness ofthe material strip or material part. By placing the upper and/or lowerroller mill in the region of the inlet at a spacing which corresponds atleast to the material thickness of the metal strip or metal part, it isensured that the front end of the metal strip or metal part does notcollide with an upper and/or lower straightening roller, as a result ofwhich damage to the upper and/or lower straightening roller as well as acrushing of the front end of the metal strip or metal part is/areavoided.

Alternatively or preferably additionally, the advancing of the upperand/or lower roller mill into the operating position is performed insuch a manner that the straightening gap in the operating position inthe region of the outlet corresponds substantially to the thickness ofthe material strip or material part.

One preferred embodiment of the method, above all in the case of anoperating angle which opens toward the outlet, is characterized in thatthe movement of the upper and/or lower roller mill into the operatingposition is performed in an incremental or step-by-step manner. As aresult of the incremental or step-by-step movement of the upper and/orlower roller mill into the operating position, it can in particular beavoided that the front end of the metal strip or metal part hits one ofthe upper straightening rollers. A deformation of the front end of themetal strip or metal part or damage to the straightening rollers canthus be avoided. At the same time, the incremental advancing into theoperating position makes it possible that the metal strip or metal partin the portion of the operating region upstream in the operatingdirection, which has already been passed by the front end of the metalstrip or metal part, is at least partially straightened. In particular,the region of the metal strip or metal part adjacent to the front end ofthe metal strip can thus be better straightened so that overall a betterstraightening result can be achieved.

A step of advancing is preferably performed with or after passing alower and/or upper straightening roller, wherein the advancing in thestep is preferably performed in such a manner that the straightening gapat a downstream upper and/or lower straightening roller correspondssubstantially to the thickness of the metal strip or metal part. Byadjusting a downstream lower and/or upper straightening roller in such amanner that the spacing corresponds substantially to the thickness ofthe metal strip or metal part, it is avoided that the front end of themetal strip or metal part collides with the subsequent upper and/orlower straightening roller and that a crushing is performed in theregion of the front end of the metal strip or metal part. At the sametime, the metal strip or metal part is moved toward the outlet in amanner guided by the operating region of the straightening machine. As aresult of the angled adjustment of the upper with respect to the lowerroller mill plane, straightening forces are furthermore exerted on themetal strip or metal part by the upper and/or lower straighteningrollers which have already been passed so that the metal strip or metalpart is correspondingly optimally straightened.

An advancing of the straightening machine is thus preferably carried outwith or after passing a lower and/or upper straightening roller in smallsteps in such a manner that, in the operating position, thestraightening gap corresponds substantially to the thickness of themetal strip or metal part finally in the region of the outlet of thestraightening machine.

The spacing of the front end of the metal strip or metal part downstreamof the sensor or the predetermined position can also serve as a triggerfor the incremental movement of the upper and/or lower roller mill intothe operating position. For example, an advancing of the front end ofthe metal strip or metal part by a certain distance or by a certain timeinterval after passing the predetermined position can be a trigger for afurther step of advancing into the operating position, wherein a furtherstep of advancing is performed after travelling a further distance orafter the expiry of a further time interval. The number of steps dependsin particular of the metal part or metal strip to be straightened, inparticular on its thickness. Alternatively or preferably additionally,the length of the operating region and the number of the upper and/orlower straightening rollers and their spacing also have an effect on thenumber of steps for the incremental advancing of the roller mills intothe operating position.

The movement of the upper and/or lower roller mill into the operatingposition can also be performed continuously. As soon as the front end ofthe metal strip or metal part has reached the predetermined position,the upper and/or lower roller mill is moved linearly or in anaccelerated manner into the operating position. The speed oracceleration of the continuous movement of the upper and/or lower rollermill into the operating position can preferably correlate with a speedof the metal strip or metal part and/or with the position of the metalstrip or metal part within the straightening machine, in particular withthe spacing of the front end of the metal strip or metal part to thepredetermined position.

In one preferred embodiment, the movement of the upper and/or lowerroller mill into the starting position is carried out at least partiallyvia a pivoting movement, preferably about a pivot axis outside theoperating region of the straightening machine. The upper and/or lowerroller mill is thus pivoted with respect to the respective other rollermill into the starting position in such a manner that the angle betweenthe upper and lower roller mill plane transitions from the operatingangle (which can also be equal to zero) into a starting angle which isdifferent from the operating angle and the non-parallel wideningaccording to the invention of the straightening gap is achieved. If theoperating angle opens toward the outlet, the straightening gap inparticular in the region of the inlet is widened to a spacing at leastin the region of the material thickness of the metal strip or metalpart, while the straightening gap in the region of the outlet can bebarely changed or not at all.

The upper and/or lower roller mill can be moved with a pure pivotingmovement or in such a manner into the starting position that a paralleldisplacement of the upper and/or lower roller mill is performed and atthe same time or consecutively a pivoting movement is performed. As aresult of this, it is made possible that the metal strip or metal partto be straightened can be easily pulled into the straightening machineand optimally straightened, wherein crushing in the region of the frontend of the metal strip is also avoided.

A straightening machine according to the invention for straightening amaterial strip or a flat metal part comprises a number of upperstraightening rollers in an upper roller mill and a number of lowerstraightening rollers in a lower roller mill which form between an inletand an outlet of the straightening machine in an operating regionbetween the upper and the lower roller mill a straightening gap inorder, in an operating position of the upper and lower roller mill, toact at least temporarily from top to bottom on the material strip ormaterial part to be straightened and guide it in an operating directionfrom the inlet to the outlet of the operating region through thestraightening machine. At least a part of the axes of the upperstraightening rollers forms an upper roller mill plane and at least apart of the axes of the lower straightening rollers spans a lower rollermill plane, wherein the upper roller mill plane and the lower rollermill plane, in the operating position, are parallel or at apredetermined operating angle to one another. In order to change or setthe straightening gap, the upper roller mill and the lower roller millare adjustable relative to one another, can be placed at least into astarting position with a widened straightening gap and can be advancedinto the starting position.

The straightening machine further comprises a controller for adjustmentof the upper and lower roller mill with respect to one another and asensor for detection of a front end of the metal strip or metal part tobe straightened and outputting a sensor signal to the controller.

According to the invention, the upper roller mill and the lower rollermill are adjustable relative to one another in such a manner that thestraightening gap during placing into the starting position is widenedto a greater extent at the inlet than at the outlet or is widened to agreater extent at the outlet than at the inlet, i.e. the upper roll millplane encloses a starting angle to the lower roller mill plane in thestarting position, which starting angle is different from the operatingangle, wherein the controller is formed in such a manner that it adjuststhe upper and/or lower roller mill from the starting position into theoperating position immediately in response to the sensor signal or witha time delay.

The straightening machine makes it possible to introduce the metal partor metal strip to be straightened in the starting position of the rollermills into the straightening machine so that a crushing or a rolling outof the front end of the metal part or metal strip is avoided. Thisimproves the quality of the metal part or metal strip. Moreover, as aresult of the placing possible according to the invention of the upperand/or lower roller mill into the starting position with widening, whichis not parallel according to the invention, of the straightening gap, inparticular in the region of the inlet of the straightening machine atthe start of the straightening process, an abutment of the front end ofthe metal part or metal strip against one of the first straighteningrollers during introduction is avoided, as a result of which thedurability of the components is improved.

The sensor is preferably arranged at the height of a predeterminedposition, or upstream in the operating direction at a spacing in frontof the predetermined position. In particular the upstream arrangement,preferably before the inlet of the straightening machine, enables simpleinstallation and maintenance of the sensor.

The predetermined position preferably lies in the region of the inlet,or corresponds to a location of one of the upper and lower straighteningroller, preferably the location of a first, second, third, fourth orfifth lower or upper straightening rollers in the operating direction.

The controller of the straightening machine is preferably formed so thatthe time delay for the adjustment of the upper and/or lower roller millinto the operating position is determined from a conveying speed of thematerial strip or material part and the spacing between the sensor andthe predetermined position. As a result of this, it is made possiblethat the sensor can be arranged outside the straightening machine andthe predetermined position can simultaneously lie within thestraightening machine.

The sensor is preferably a physical sensor, in particular an optical orinductive sensor. The optical sensor involves in particular a lightbarrier.

A further preferred embodiment of the straightening machine ischaracterized in that the upper roller mill is pivotable with respect tothe lower roller mill and/or the lower roller mill is pivotable withrespect to the upper roller mill about a pivot axis, wherein the pivotaxis preferably lies outside the operating region of the straighteningmachine.

The upper roller mill is preferably retained in guides of thestraightening machine and can be moved up and down on the guidesrelative to the lower roller mill, wherein the guides are formed in sucha manner that the upper roller mill is adjustable and/or pivotableasymmetrically on the guides. The attachment of the upper roller mill bymeans of these guides makes it possible that the forces acting on themetal strip or metal part to be straightened can be correspondinglyabsorbed and a movement of the upper roller mill with small tolerancescan simultaneously be carried out. The guides furthermore enable atranslational movement of the upper roller mill toward the lower rollermill and away from it.

In an even further preferred embodiment of the straightening machine,the upper roller mill is pivotable by means of a pivoting apparatus,wherein the pivoting apparatus is operatively connected at least to theguides which are arranged in the region of the outlet. In particular, acompact design can be achieved in this manner, in the case of which allthe key components for pivoting and also for translational movement ofthe upper roller mill are arranged thereon or are operatively connectedthereto. As a result of this, a retrofitting of existing systems with apivotable upper roller mill is also enabled.

BRIEF DESCRIPTION OF THE DRAWINGS

An exemplary embodiment of a straightening machine configured accordingto the invention, on the basis of which an exemplary embodiment of amethod according to the invention is also explained, is described belowon the basis of the enclosed drawings. In the drawings:

FIG. 1 shows a schematic side view of the straightening machine in thestarting position; and

FIG. 2 shows a schematic side view of a straightening machine in theoperating position.

DETAILED DESCRIPTION

A straightening machine 1 according to the invention is representedschematically in a side view in a starting position in FIG. 1 . Thestraightening machine 1 comprises an upper roller mill 2 on which amultiplicity of upper straightening rollers 3, in the present case fourupper straightening rollers 3, is arranged. A lower roller mill 5 whichalso comprises a multiplicity of lower straightening rollers 6, in thepresent case five lower straightening rollers 6, is arranged oppositethe upper roller mill 2. The upper and lower straightening rollers 3, 6are in the upper and lower roller mill 2, 5 equidistant and arranged insuch a manner that an upper straightening roller 3 engages into theregion of the space between two lower straightening rollers 6.

A lower roller mill plane 7 runs through the axes 9 of the lowerstraightening rollers 6; an upper roller mill plane 4 runs in ananalogous manner through the axes 9 of the upper straightening rollers3. Alternatively, the upper roller mill plane 4 can only partiallycomprise the axes 9 of the upper straightening rollers 3, in particularif a first upper straightening roller 3 in the operating direction 14 israised with respect to the further upper straightening rollers 3. Thelower roller mill plane 7 can likewise only partially comprise the axes9 of the lower straightening rollers 6 in particular if a last lowerstraightening roller 6 in the operating direction is lowered.

The upper roller mill 2 is guided on four guides 20 which are configuredas stud bolts, and it can be moved along these guides 20 translationallyto the lower roller mill 5 and moved away therefrom. The upper rollermill 2 is guided in the guides 20 in such a manner that the upper rollermill 5 is adjustable within the guides 20 asymmetrically between inlet12 and outlet 13 of the straightening machine 1 and/or is pivotableabout an axis which runs parallel to the roller mill planes 4, 7.

For this purpose, there is arranged on the upper roller mill 2 apivoting apparatus 21, by means of which the upper roller mill 2 ispivotable with respect to the lower roller mill 5 about a pivot axis, asa result of which the upper roller mill plane 4 is also changed withrespect to the lower roller mill plane 7. The pivoting apparatus 21 isin this case operatively connected to the guides 20, arranged at theoutlet 13, of the straightening machine 1. In addition to the pivotingapparatus 21, the upper roller mill 2 can be moved up and down withrespect to the lower roller mill 5 in the guides 20 parallel to thelower roller mill 5.

In the starting position of the straightening machine 1, as isrepresented in FIG. 1 , the lower roller mill plane 7 and the upperroller mill plane 4 enclose a starting angle 10 which opens toward theoutlet 13. This starting angle 10 between the upper and lower rollermill plane 4, 7 in the starting position is formed in this case so thatit is smaller than an operating angle 8 in the operating position (FIG.2 ), i.e. the straightening gap 11 is widened to a greater extent incomparison with the operating position at the inlet 12 than at theoutlet 13. With a pivoting of the upper roller mill 2 with respect tothe lower roller mill 5 about the pivot axis, the straightening gap 11is widened along the operating region of the straightening machine 1between inlet 12 and outlet 13 so that the spacing of the upperstraightening rollers 3 with respect to the lower straightening rollers6 is also increased overall in comparison with the operating position.In the starting position, the straightening gap 11 in the region of theinlet 12 is formed in such a manner that it corresponds at least to thethickness of the metal part 16 to be straightened. For further wideningof the inlet 12 of the straightening machine 1, the upper roller mill 2can, in addition to the pivoting movement about the pivot axis, alsoadditionally be displaced parallel along the guides 20. The movement ofthe upper roller mill 2 is controlled or regulated via a controller 22.In addition to the upper roller mill 2, the pivoting apparatus 21 isalso operatively connected to the controller 22.

For the straightening of the metal part 16, the straightening machine 1is firstly brought into the starting position, as represented in FIG. 1, in which the straightening machine 1 has a widened straightening gap11 and a starting angle 10 between the upper and lower roller mill plane4, 7 which opens toward the outlet 13, but is formed to be smaller thanthe operating angle 8.

A flat metal part 16 to be straightened firstly passes a sensor 18during transport into the straightening machine 1 in operating direction14, which sensor 18 detects a front end 17 of the metal part 16. Thesensor 18 is formed in the present case as a light barrier and isarranged in a region upstream of the inlet 12 in operating direction 14.As a result of the arrangement outside the straightening machine 1, thesensor 18 is easily accessible in comparison with an installation of thesensor 18 within the straightening machine 1 and enables fault-freedetection of the front end 17 of the metal part 16. The sensor 18arranged in such a manner can furthermore where necessary be adaptedflexibly and quickly to different metal strips or parts to bestraightened, in particular of a different thickness. Alternatively, itis also possible that the sensor 18 is arranged within the straighteningmachine 1, in particular in the region of the inlet 12 or one of thefirst upper or lower straightening rollers 3, 6. The sensor 18 is alsooperatively connected to the controller 22 and outputs a correspondingsensor signal to the controller 22 during detection of the front end 17of the metal part 16.

The front end 17 of the metal part 16 firstly runs through the inlet 12of the straightening machine 1 along the conveying path of the metalpart 16 into the straightening machine 1, along which the metal part 16is conveyed with a constant speed. By widening the straightening machine1 in the region of the inlet 12 at least into the region of the materialthickness of the metal part 16 by pivoting the upper roller mill 2 withrespect to the lower roller mill 5, it is ensured that the front end 17of the metal part 16 does not collide with an upper straightening roller3 or the upper roller mill 2. Moreover, during entry into thestraightening machine 1, the region around the front end 17 of the metalpart 16 initially does not experience any forces which could lead to adeformation of the front end 17, in particular to crushing. As soon asthe front end 17 of the metal part 16 has reached or passed apredetermined position 15 which in the present case corresponds to thelocation of the axis 9 of the second upper straightening roller inoperating direction 14, the upper roller mill 2 is moved incrementallyfrom the starting position, as is represented in FIG. 1 , into theoperating position, as is represented in FIG. 2 .

In the operating position, the upper roller mill plane 4 and the lowerroller mill plane 7 enclose an operating angle 8 to one another. Astraightening gap 11 is formed between the upper and lower straighteningrollers 3, 6 in the operating position over the operating region betweeninlet 12 and outlet 13, in which straightening gap 11 correspondingforces are exerted at least temporarily via the upper and lowerstraightening rollers 3, 6 from top to bottom on the metal part 16 to bestraightened. In this case, the metal part 16 is bent between the upperand lower straightening rollers 3, 6 arranged offset to one another,wherein a more pronounced bending of the metal part 16, beyond its yieldpoint, occurs in the region of the inlet 12. As a result of the bendingof the metal part 16 in the straightening gap 11, bending and tension inthe metal part 16 are reduced. A lower degree of bending of the metalpart 16 occurs at each subsequent upper or lower straightening roller 3,6 in operating direction 14 so that a straightened and flat metal part16 is conveyed out of the straightening machine 1 at the outlet 13. Thefurther processing of the metal part 16 is significantly simplified andimproved by the straightening.

In the operating position, the operating angle 8 between the upper andlower roller mill plane 4, 7 is formed in such a manner that, in theregion of the outlet 13, the straightening gap 11 correspondssubstantially to the material thickness of the metal part 16 to bestraightened and that, in the region of the inlet 12, the upper andlower straightening rollers 3, 6 in the straightening gap 11 have aspacing smaller than the material thickness of the metal part 16.

The axes 9 of the lower straightening rollers 6 lie here in the lowerroller mill plane 7 and the axes 9 of the upper straightening rollers 3span the upper roller mull plane 4, which opens toward the outlet 13. Asa result of this, it is achieved that the metal part 16 to bestraightened in the straightening machine 1 is bent to a lesser extenttoward the outlet 13 and is only slightly deformed.

The movement or advancing of the upper roller mill 2 from the startingposition, as represented in FIG. 1 , into the operating position, asrepresented in FIG. 2 , is primarily performed via a pivoting movementof the upper roller mill 2 by means of the pivoting apparatus 21. Thepivoting movement is performed incrementally in several steps so that itcan be ensured that the front end 17 of the metal part 16 does notcollide with one of the upper straightening rollers 3 during conveyinginto the straightening machine 1. As a result of the incrementalmovement of the upper roller mill 2 into the operating position, it isfurthermore ensured that no crushing occurs in the region of the frontend 17 of the metal part 16.

The incremental advancing from the starting position into the operatingposition is performed as a function of the conveying of the metal part16 through the straightening machine 1. A step of further advancing intothe operating position is thus triggered by virtue of the fact that thefront end 17 of the metal part 16 passes an upper straightening roller 3arranged after the predetermined position 15. The advancing is performedin the respective step by virtue of the fact that the upper roller mill2 is pivoted so that an upper straightening roller 3 downstream of thepassed upper straightening roller 3 is positioned in such a manner thata spacing to the lower straightening rollers 6 arises which correspondssubstantially to the material thickness of the metal part 16. It is thusensured at all times that the front end 17 of the metal part 16 does notcollide with one of the upper straightening rollers 3. The incrementaladvancing is performed until the front end 17 of the metal part hasreached the outlet 13 and the straightening gap 11 in the region of theoutlet 13 corresponds substantially to the material thickness of themetal part 16. The straightening gap 11 in the region toward the inlet12 is furthermore advanced to a greater extent with each step, hencecorresponding forces already act on the metal part 16 during advancing,as a result of which the straightening result is improved.

The movement of the upper roller mill 2 into the operating position isstarted after the front end 17 of the metal part 16 reaches thepredetermined position 15. As represented in FIG. 1 , the predeterminedposition 15 is located within the straightening machine 1 at the heightof the axis 9 of the second upper straightening roller 3 downstream inthe operating direction 14. As a result of the location of thepredetermined position 15 within the straightening machine 1 in thevicinity of the inlet 12, it is likewise ensured that the front end 17of the metal part 16 is not crushed and rolled out by excessivestraightening forces and nevertheless the metal part 16 is optimallystraightened. It is achieved in particular as a result of the pivotingmovement of the upper roller mill 2 into the operating position thatstraightening forces are exerted at least partially on the region of themetal part 16 adjoining the front end 17 of the metal part 16, andindeed immediately after the predetermined position 15 has been passedby the front end 17 and the advancing into the operating position hasbeen performed. Alternatively, the predetermined position 15 can liee.g. also directly at the inlet 12 into the straightening machine 1.

As also represented in FIG. 1 , the sensor 18 for detecting the frontend 17 of the metal part 16 is not arranged directly at thepredetermined position 15, but rather has a spacing 19 upstream inoperating direction 14 to the predetermined position 15. In order todetermine the point in time at which the front end 17 of the metal part16 reaches the predetermined position 15, a time delay is determined viathe spacing 19 and the conveying speed of the metal part 16, after whichtime delay the front end 17 has reached the predetermined position 15after detection of the corresponding sensor signal by the sensor 18 andthe upper roller mill 2 is then adjusted incrementally from the startingposition into the operating position.

LIST OF REFERENCE NUMBERS

-   -   1 Straightening machine    -   2 Upper roller mill    -   3 Upper straightening roller    -   4 Upper roller mill plane    -   5 Lower roller mill    -   6 Lower straightening roller    -   7 Lower roller mill plane    -   8 Operating angle    -   9 Axis (of 3, 6)    -   10 Starting angle    -   11 Straightening gap    -   12 Inlet    -   13 Outlet    -   14 Operating direction    -   15 Predetermined position    -   16 Metal part    -   17 Front end    -   18 Sensor    -   19 Spacing    -   20 Guide    -   21 Pivoting apparatus    -   22 Controller

1. A method for straightening a material strip or a flat material partcomposed of a material which is plasticizable using a straighteningmachine (1) with a number of upper straightening rollers (3) in an upperroller mill (2) and a number of lower straightening rollers (6) in alower roller mill (5), which form a straightening gap (11) between aninlet (12) and an outlet (13) of the straightening machine (1) in anoperating region between the upper and the lower roller mill (2, 5), theupper and the lower straightening rollers (3, 6) in an operatingposition of the upper and lower roller mill (2, 5) act at leasttemporarily from top to bottom on the material strip or material part tobe straightened and guide the material strip or part in an operatingdirection (14) from the inlet (12) to the outlet (13) of the operatingregion through the straightening machine (1), at least a part of axes(9) of the upper straightening rollers (3) form an upper roller millplane (4) and at least a part of axes (9) of the lower straighteningrollers (6) forms lower roller mill plane (7), which in the operatingposition are parallel or at a predetermined operating angle (8) to oneanother, the method comprising: in order to change the straightening gap(11), at least one of adjusting the upper roller mill (2) relative tothe lower roller mill (5) or adjusting the lower roller mill (5)relative to the upper roller mill (2); and prior to or at a start of astraightening process, placing at least one of the upper or lower rollermill (2, 5) into a starting position at least until a front end of thematerial strip or material part has run into the inlet (12) of anoperating region of the straightening machine (1) by widening thestraightening gap (11) to a greater extent that at the outlet (13),widening the straightening gap (11) to a greater extent at the outlet(13) than at the inlet (12); and for the further straightening process,advancing at least one of the upper or lower roller mill (2, 5) into anoperating position.
 2. The method as claimed in claim 1, wherein thestraightening gap (11) during placing into the starting position iswidened to a greater extent at the inlet (12) than at the outlet (13) ifthe operating angle (8) opens toward the outlet (13) or the upper rollermill plane (4) is parallel to the lower roller mill plane (7), or thestraightening gap (11) during placing into the starting position iswidened to a greater extent at the outlet (13) than at the inlet (12) ifthe operating angle (8) opens toward the inlet (12).
 3. The method asclaimed in claim 1, further comprising the method steps: (A) placing atleast one of the upper or lower roller mill (2, 5) into the startingposition; and (B) advancing at least one of the upper or lower rollermill (2, 5) into the operating position, wherein method step B isperformed when or after the front end (17) of the material strip ormaterial part (16) has reached a predetermined position (15) in theoperating region.
 4. The method as claimed in claim 3, wherein a regionof the inlet (11), or a location of one of the lower or upperstraightening rollers (3, 6) is used as the predetermined position (15).5. The method as claimed in claim 3, wherein the front end (17) of thematerial strip or material part is detected by a sensor (18).
 6. Themethod as claimed in claim 5, wherein the sensor (18) is arranged at thepredetermined position (15) and method step B is performed immediatelyafter detection of the front end (17) of the material strip or materialpart (16) by the sensor (18).
 7. The method as claimed in claim 5,wherein the sensor (18) is arranged at a spacing (19) upstream of thepredetermined position (15) in the operating direction (14), and themethod further comprises determining a time delay until thepredetermined position (15) of the front end (17) of the material stripor material part (16) is reached from a conveying speed of the materialstrip or material part and the spacing (19) between the sensor (18) andthe predetermined position (15), and method step B is performed with orafter the end of the time delay after detection of the front end (17) ofthe material strip or material part by the sensor (18).
 8. The method asclaimed in claim 1, wherein at least one of a) the placing of at leastone of the upper or lower roller mill (2, 5) into the starting positionis performed such that the straightening gap (11) in a region of theinlet (12) corresponds at least to a thickness of the material strip ormaterial part (16) or b) the advancing of at least one of the upper orlower roller mill (2, 5) into the operating position is performed suchthat the straightening gap (11) in a region of the outlet (13)corresponds substantially to the thickness of the material strip ormaterial part (16).
 9. The method as claimed in claim 1, wherein atleast one of a) the placing of at least one of the upper or lower rollermill (2, 5) into the starting position is performed such that thestraightening gap (11) in a region of the outlet (13) corresponds atleast to a thickness of the material strip or material part (16) or 12)the advancing of at least one of the upper or lower roller mill (2, 5)into the operating position is performed such that the straightening gap(11) in a region of the inlet (12) corresponds substantially to thethickness of the material strip or material part (16).
 10. The method asclaimed in claim 1, wherein the advancing of at least one of the upperor lower roller mill (2, 5) into the operating position is performedcontinuously.
 11. The method as claimed in claim 1, wherein theadvancing of at least one of the upper or lower roller mill (2, 5) intothe operating position is performed in an incremental manner.
 12. Themethod as claimed in claim 11, wherein one step of the advancing isperformed with or after passing at least one of one said lower or upperstraightening roller (3, 6), and the advancing is performed in the stepsuch that the spacing of the upper and lower straightening rollers (3,6) at a downstream said upper and/or lower straightening roller (3, 6)corresponds substantially to the thickness of the material strip ormaterial part (16).
 13. The method as claimed in claim 1, wherein atleast one of the upper roller mill (2) or the lower roller mill (5) ismoved at least partially via a pivoting movement into at least one ofthe starting position or the operating position.
 14. A straighteningmachine (1) for straightening a material strip or a flat materialcomposed of a material which can be plasticized, the straighteningmachine comprising: a number of upper straightening rollers (3) in anupper roller mill (2); a number of lower straightening rollers (6) in alower roller mill (5); a straightening gap formed between an inlet (12)and an outlet (13) of the straightening machine (1) in an operatingregion between the upper and the lower roller mills (2, 5), thestraightening gap (11), in an operating position of the upper and lowerroller mills (2, 5) being configured to act at least temporarily fromtop to bottom on the material strip or material part to be straightenedand guide the material strip or material part in an operating direction(14) from the inlet (12) to the outlet (13) of the working regionthrough the straightening machine (1); at least a part of axes (9) ofthe upper straightening rollers (3) form an upper roller mill plane (4)and at least a part of axes (9) of the lower straightening rollers (6)form a lower roller mill plane (7) which in the operating position areparallel or at a predetermined operating angle (8) to one another; inorder to change the straightening gap (11), the upper roller mill (2)and the lower roller mill (5) are adjustable relative to one another,and are placeable at least into a starting position with a widenedstraightening gap (11) and are advanceable into the starting position; acontroller (22) configured to adjust the upper and lower roller mills(2, 5) with respect to one another; a sensor (18) for detection of afront end (17) of the material strip or material part (16) to bestraightened, the sensor configured to output a sensor signal to thecontroller (22); the controller (22) being further configured to adjustat least one of the upper or lower roller mill (2, 5) from the startingposition into the operating position immediately after or with a timedelay to the sensor signal; and the upper roller mill (2) and the lowerroller mill (5) are adjustable relative to one another such that thestraightening gap (11) during placing into the starting position iswidened to a greater extent at the inlet (12) than at the outlet (13),or is widened to a greater extent at the outlet (13) than at the inlet(12).
 15. The straightening machine as claimed in claim 14, wherein thecontroller (22) is configured to widen the straightening gap (11) duringplacing into the starting position at the inlet (12) to a greater extentthan at the outlet (13) if the operating angle (8) opens toward theoutlet (13) or the upper roller mill plane (4) is parallel to the lowerroller mill plane (7), or to widen the straightening gap (11) duringplacing into the starting position at the outlet (13) to a greaterextent than at the inlet (12) if the operating angle (8) opens towardthe inlet (12).
 16. The straightening machine as claimed in claim 14,wherein the upper roller mill plane (4) encloses a starting angle (10)to the lower roller mill plane (7) in the starting position, and saidstarting angle (10) is not equal to the operating angle (8).
 17. Thestraightening machine as claimed in claim 14, wherein the sensor (18) isarranged at a height of a predetermined position (15), or upstream inthe operating direction (14) at a spacing (19) in front of thepredetermined position (15), wherein the predetermined position (15)lies in a region of the inlet (12), or corresponds to a location of oneof the lower or upper straightening rollers.
 18. The straighteningmachine as claimed in claim 17, wherein the controller (22) isconfigured such that the time delay for the adjustment of at least oneof the upper or lower roller mill (2, 5) into the operating position isdetermined from a conveying speed of the material strip or material partand the spacing (19) between the sensor (18) and the predeterminedposition (15).
 19. The straightening machine as claimed in claim 14,wherein the sensor (18) is a physical sensor.
 20. The straighteningmachine as claimed in claim 14, wherein at least one of a) the upperroller mill (2) is pivotable with respect to the lower roller mill (5)or b) the lower roller mill (5) is pivotable with respect to the upperroller mill (2) about a pivot axis, and the pivot axis lies outside anoperating region of the straightening machine (1).
 21. The straighteningmachine as claimed in claim 14, wherein the upper roller mill (2) isretained in guides (20) of the straightening machine (1) and is movableup and down on the guides (20) relative to the lower roller mill (3),and the guides (20) are formed such that the upper roller mill (2) is atleast one of adjustable or pivotable asymmetrically on the guides (20).